Forms, Circulars & Regulations

Groundwater Protection

Montanans rely heavily on groundwater as the primary source of drinking water for many rural domestic water supplies as well as public water systems. Groundwater is also important for irrigation, livestock, and indirectly for thermoelectric power. Montana’s programs for the protection and remediation of groundwater are driven by the need to keep groundwater safe from contamination and to protect and support the current and future uses of groundwater

Although DEQ has primary responsibility for groundwater protection, a number of programs across the state aid in the protection of groundwater. Several agencies, the Department of Environmental Quality, Department of Natural Resources and Conservation, and the Department of Agriculture implement the majority of federal and state programs relating to groundwater.

Montana depends on Groundwater for much of its drinking water supply from either public sources or private wells. It is important to understand how groundwater is protected and made safe for drinking.

Groundwater Quality Standards

Drinking water standards and guidelines place a ceiling on contaminant levels in the drinking water supplied by public water systems, regardless of whether the source is Groundwater or surface water.

There is no regulation for ensuring that private wells meet safe drinking water standards. However, private well owners can have their wells tested and use federal drinking water standards as a guide for assessing water quality.

Water systems that have groundwater sources may be susceptible to fecal contamination. In many cases, fecal contamination can contain disease causing pathogens. The Groundwater Rule (GWR) applies to public water systems that use groundwater as a source of drinking water and that may be susceptible to fecal contamination. The rule also applies to any system that delivers surface and groundwater to consumers where the groundwater is added to the distribution system without treatment. The purpose of the Groundwater Rule is to reduce disease incidence associated with harmful microorganisms in drinking water.

Requirements of the Groundwater Rule

Periodic sanitary surveys of groundwater systems require the evaluation of eight critical elements and the identification of significant deficiencies (e.g., a well located near a leaking septic system).

Source water monitoring to test for the presence of E. coli, enterococci, or coliphage in the sample. There are two monitoring provisions: Triggered monitoring for systems that do not already provide treatment that achieves at least 99.99 percent (4-log) inactivation or removal of viruses and that have a total coliform-positive routine sample under Total Coliform Rule sampling in the distribution system. Assessment monitoring-As a complement to triggered monitoring, Montana has the option to require systems, at any time, to conduct source water assessment monitoring to help identify high risk systems.

Assessment monitoring as a complement to triggered monitoring. Montana has the option to require systems, at any time, to conduct source water assessment monitoring to help identify high risk systems.

Corrective actions required for any system with a significant deficiency or source water fecal contamination. The system must implement one or more of the following correction action options:

Private well owners are responsible for the quality of their water, and no regulatory oversight exists to ensure water quality. However, there are numerous resources for private well owners to assist them in maintaining high quality drinking water.

All groundwater sources in Montana are to be assessed as either Groundwater (GW) or Groundwater Under the Direct Influence of Surface Water (GWUDISW). See Circular PWS-5, for the complete GWUDISW rule.

'Under the direct influence of surface water' means the groundwater source is located close enough to nearby surface water, such as a river or lake, to receive direct surface water recharge. Since a portion of the groundwater source's recharge is from surface water, the groundwater source is considered at risk of contamination from pathogens such as Giardia lamblia, cryptosporidium, and viruses, which are not normally found in true Groundwaters.

Sources most likely to be under the direct influence of surface water are:

Infiltration gallery systems and horizontal wells;

Spring systems;

Wells located near surface waters.

A source of subsurface water (well, spring, horizontal well, or infiltration gallery) is presumed to be groundwater at the start of the process. It is only if evidence appears that there may be the direct influence of surface water in the source that the designation of the source could change to GWUDISW.

The first step in determining if a source is under direct influence of surface water is for DEQ staff to complete a preliminary assessment form. Based on the results of the preliminary assessment, the source will either be characterized as groundwater or be required to undergo further assessment.

If the source is classified as groundwater under direct influence of surface water (GWUDISW), it must meet the same treatment technologies as surface water and the system must install filtration and disinfection in accordance with the surface water treatment rule.

The Montana Water Quality Act (§75-5-605 ) requires a valid permit for the following activities:

(a) construct, modify, or operate a disposal system that discharges into any state waters;

(b) construct or use any outlet for the discharge of sewage, industrial wastes, or other wastes into any state waters; or

(c) discharge sewage, industrial wastes, or other wastes into any state waters.

MGWPCS permits are for discharge to state groundwaters. They are not applicable for discharges occurring within the boundaries of federally recognized Indian Lands. For additional information on discharges occurring within Indian Lands please refer to the USEPA Underground Injection Control Program

MGWPCS permits may also not be applicable for discharges located near state surface waters. For additional information on surface water discharge permits, please refer to the Surface Water Discharge (MPDES) program.

An individual MGWPCS permit is a stand-alone permit issued for a site-specific activity. Each individual permit may differ as they are based on the specifics of each discharge site and of each proposed discharge activity.

Each individual permit is placed into a category based on the type of wastewater to be discharged; either domestic (e.g. sinks, toilets, showers) or non-domestic (industrial or other wastewater). Please see below for application information.

Maintenance of an existing permit is sometimes needed in order to keep the permit up to date with proposed facility or administration changes. A Modifications may be classified as either a minor or major depending on the proposed changes.

Major Modifications are typically required when the permittee plans to alter their collection system, treatment facility, or disposal structures (e.g. addition of a discharging structure, increase in design capacity). A modification may not be required when replacing like-for-like equipment, or improving the existing treatment methods.

The application procedures for major modification of an individual permit mirrors the administrative procedure in applying for a new permit. For more information, please refer to the Individual Permit Application Information.

Minor Modifications are typical when the permittee plans on undergoing minor administrative changes such as transfer of permit ownership. In order to transfer ownership, a complete PTN form, along with a $500 minor modification fee is required.

About Us

The Montana Department of Environmental Quality is charged with protecting a clean and healthy environment as guaranteed to our citizens by our State Constitution. Our ultimate goal is to protect public health and to maintain Montana's
high quality of life for current and future generations.